174 The Mechanistic Conception of Life 



and this explanation casts light on the nature of the protective 

 or antagonistic action of salts. For the antagonistic action of 

 a salt of lead or zinc against the toxic action of sodium chloride 

 can only consist in the lead salt protecting the embryo against 

 the toxic action of the NaCl. But how is this protective 

 action possible? 



We have mentioned that if we put the young fish, imme- 

 diately after hatching, into a pure m/2 solution of sodium 

 chloride the animals die very quickly, but that they live 

 indefinitely in the sodium chloride solution if we add both 

 CaCl, and KCl. How does it happen that for the embryo, as 

 long as it is in the egg shell, the addition of CaCl, to the NaCl 

 solution suffices, while if the fish is out of the shell the addition 

 of CaCl, alone is no longer sufficient and the addition of KCl 

 also becomes necessary ? Moreover, if we try to preserve the 

 life of the fish after it is taken out of the egg in an m/2 sodium 

 chloride solution by adding ZnSO^, or lead acetate, to the solu- 

 tion we find that the fish die even much more quickly than 

 without the addition.^ 



If we look for the cause of this difference our attention 

 is called to the fact that the fish, as long as it is in the egg, is 

 separated from the surrounding solution by the egg membrane. 

 This egg membrane possesses a small opening, the so-called 

 micropyle, through which the spermatozoon enters into the egg. 

 I have gained the impression that this micropyle is not closed 

 as tightly immediately after fertilization as later on, since the 

 newly fertilized egg is killed more rapidly by an m/2 solution of 

 NaCl than it is killed by the same solution one or two days 

 after fertilization. One can imagine that the micropyle con- 

 tains a wad of a colloidal substance which is hardened gradually 

 to a leathery consistency if the egg remains in the sea-water. 



1 R. Lillie has found that in the larvae of Arenicola a slight antagonism 

 between NaCl and ZnSOj can be proved. This shows that the general laws of 

 antagonism between two salts differ in degree but not in principle in the living 

 organism and the dead envelop of the fish egg. 



